The invention relates to helically coiled tube heat exchangers and, more particularly, to an improved technique for stabilizing the tubes in an array by spring loading the tubes within a channel structure, and the like.
There is a need for heat exchangers in which the tubing is coiled in an helical manner. Naturally, the environment within these heat exchangers, i.e., boiling fluid and high velocity flow conditions, frequently requires that the coiled tubes should be securely anchored to prevent undesirable vibration attendant damage. Because these heat exchangers often are operated at high temperatures, there also is a somewhat conflicting need for a tube mounting structure that will provide the tube with sufficient latitude for thermal expansion and contraction.
Through the years, a number of proposals have been advanced for resolving this important engineering problem. The patents identified in the following are a representative sample of a number of these proposals:
U.S. Pat. No. 3,989,105 shows layers of undulating tubes fitted between concentric hoops and tube braces that are wedged between the adjacent tubes in each layer.
U.S. Pat. No. 3,782,455 shows a series of circumferential bars in a concentric arrangement for grasping tubes which are received in indentations that are formed in the bars.
U.S. Pat. No. 3,677,339 describes a structure in which the tubes are wedged between aligned spacer bars. Each of these spacer bars has projecting lugs that straddle the adjacent tube and engage a lock strip for securing the coil to the associated spacer bar.
U.S. Pat. No. 3,554,168 discloses tube support members that are in frictional engagement in order to provide a sliding contact that will permit thermal expansion.
U.S. Pat. No. 3,545,537 relates to thin plates that support recessed bars which engage and sustain heat exchanger tubes.
U.S. Pat. No. 3,545,534 shows apertured and slotted support members to which are fastened attachments that have tube-receiving surfaces.
U.S. Pat. No. 3,509,939 discloses a conical hollow displacement member from which radial arms protrude. The radial arms, in turn, sustain carrying rods that support the tubes in question.
U.S. Pat. No. 3,286,767 describes a technique for clamping the tubes in a support member.
U.S. Pat. No. 3,026,858 is directed to water cooled tube supports in which the tubes lay upon rollers to permit thermal expansion and contraction.
U.S. Pat. No. 2,884,911 shows U-shaped members that sustain plate members which have recesses for receiving the heat exchanger tubes.
U.S. Pat. No. 2,402,209 shows finned tubes that are clamped between corrugated strips.
U.S. Pat. No. 2,175,555 describes still another support structure in which the intermediate supports have sections with prongs for embracing the individual tubes.
U.S. Pat. No. 1,973,129 discloses rigid blocks that have sockets which are individual to the tube runs and in which the tubes are received.
All of these foregoing patents attempt to solve one problem at the expense of a solution to the other problem. Thus, the tubes shown in a number of these patents are rigidly mounted in the support structure to overcome possible vibration difficulties. As mentioned above, however, a rigid mounting of this nature tends to promote stresses that are attributable to thermal expansion and contraction.
On the other hand, to simply lay the tubing on rollers or to place it in a loose support arrangement may provide a degree of compensation for thermal expansion and contraction. This loose assembly is nevertheless likely to invite vibration and attendant damage.
Consequently, there is a definite need to reconcile these conflicting requirements with a structure that is sturdy, relatively inexpensive and easy to install and maintain.